16.1.5
Genetic Factors 2
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Evaluation of Other Contributing Factors
It has proven very difficult to establish how influential genes are in aggressive behaviour. This is due to the difficulty of studying them in isolation from environmental factors. It is also likely that multiple genes are involved.

Environmental factors
- One major reason for this difficulty is the problems researchers have in separating genetic and environmental factors.
- An individual may possess a gene associated with aggression, but that behaviour may only expressed if the environmental conditions are favourable.

McDermott et al. (2009)
- McDermott et al. (2009) showed that participants with the low activity MAOA gene behaved aggressively in laboratory-based money allocation games, but only when they were provoked, otherwise, they were no more aggressive than other participants.

Multi-genes
- There are probably a number if genes involved in aggressive behaviour rather than just a single gene.
- Vassos et al. (2014) conducted a meta-analysis and could find no evidence of an association between any single gene and aggression.
- This suggests that several genes are involved.

5-HTT
- Researchers are also looking at the influence of other genes.
- The study by Stuart et al. (2014) found that IPV was associated with both the low-activity form of MAOA gene and with the serotonin transporter gene (5-HTT).
- 5-HTT is another gene that influences serotonin activity in the brain.
- They found that it was the combination of these two genes that was most closely linked with IPV.
Methodological Evaluations of Genetic Factors
It has proven very difficult to establish how influential genes are in aggressive behaviour. Some of these difficulties stem from methodological issues surrounding research into aggression.

Measuring aggression
- There are problems with the way aggression is measured.
- Methods of measuring aggression differ significantly between studies.
- This affects reliability and validity.

Types of study
- Investigations of aggression often use self-reports, parent and teacher reports, and direct observations.
- This makes it very difficult to draw valid conclusions about the role of genetic factors.

Ethics
- Many of the studies into aggression have been conducted using animals.
- The hypothesis that the MAOA gene might play a role in human aggression originated from research with mice which used genetic deletion techniques.
- This is an experimental manipulation where researchers knock out single genes.
- This lets them observe subsequent effects on aggression.

Godor et al (2014)
- Godor et al (2014) showed that MAOA knockout mice have significantly increased brain serotonin levels and are hyper-aggressive.
- When serotonin was blocked by the drug fluoxetine, the mice reverted to their non-aggressive behaviour.
1Social Influence
1.1Social Influence
2Memory
2.1Memory
3Attachment
3.1Attachment
4(2026 Exams) Psychopathology
4.1Psychopathology
5(2027 Exams) Clinical Psychology & Mental Health
5.1Clinical Psychology & Mental Health
6Approaches in Psychology
6.1Approaches in Psychology
6.2Comparison of Approaches (A2 only)
7Biopsychology
7.1Biopsychology
8Research Methods
8.1Research Methods
8.2Scientific Processes
8.3Data Handling & Analysis
9Issues & Debates in Psychology (A2 only)
9.1Issues & Debates in Psychology (A2 only)
10Option 1: Relationships (A2 only)
10.1Relationships: Sexual Relationships (A2 only)
10.2Relationships: Romantic Relationships (A2 only)
10.3(2026 Exams) Relationships: Virtual (A2 only)
10.4(2027 Exams) Relationships: Online (A2 only)
11Option 1: Gender (A2 only)
11.1(2026 Exams) Gender (A2 only)
11.2(2027 Exams) Gender (A2 only)
12Option 1: Cognition & Development (A2 only)
12.1Cognition & Development (A2 only)
13Option 2: Schizophrenia (A2 only)
13.1Schizophrenia: Diagnosis (A2 only)
13.2Schizophrenia: Treatment (A2 only)
14Option 2: Eating Behaviour (A2 only)
14.1Eating Behaviour (A2 only)
15Option 2: Stress (A2 only)
15.1Stress (A2 only)
16Option 3: Aggression (A2 only)
16.1Aggression: Physiological (A2 only)
16.2Aggression: Social Psychological (A2 only)
17Option 3: Forensic Psychology (A2 only)
17.1Forensic Psychology (A2 only)
18Option 3: Addiction (A2 only)
18.1Addiction (A2 only)
18.2Treating Addiction (A2 only)
Jump to other topics
1Social Influence
1.1Social Influence
2Memory
2.1Memory
3Attachment
3.1Attachment
4(2026 Exams) Psychopathology
4.1Psychopathology
5(2027 Exams) Clinical Psychology & Mental Health
5.1Clinical Psychology & Mental Health
6Approaches in Psychology
6.1Approaches in Psychology
6.2Comparison of Approaches (A2 only)
7Biopsychology
7.1Biopsychology
8Research Methods
8.1Research Methods
8.2Scientific Processes
8.3Data Handling & Analysis
9Issues & Debates in Psychology (A2 only)
9.1Issues & Debates in Psychology (A2 only)
10Option 1: Relationships (A2 only)
10.1Relationships: Sexual Relationships (A2 only)
10.2Relationships: Romantic Relationships (A2 only)
10.3(2026 Exams) Relationships: Virtual (A2 only)
10.4(2027 Exams) Relationships: Online (A2 only)
11Option 1: Gender (A2 only)
11.1(2026 Exams) Gender (A2 only)
11.2(2027 Exams) Gender (A2 only)
12Option 1: Cognition & Development (A2 only)
12.1Cognition & Development (A2 only)
13Option 2: Schizophrenia (A2 only)
13.1Schizophrenia: Diagnosis (A2 only)
13.2Schizophrenia: Treatment (A2 only)
14Option 2: Eating Behaviour (A2 only)
14.1Eating Behaviour (A2 only)
15Option 2: Stress (A2 only)
15.1Stress (A2 only)
16Option 3: Aggression (A2 only)
16.1Aggression: Physiological (A2 only)
16.2Aggression: Social Psychological (A2 only)
17Option 3: Forensic Psychology (A2 only)
17.1Forensic Psychology (A2 only)
18Option 3: Addiction (A2 only)
18.1Addiction (A2 only)
18.2Treating Addiction (A2 only)
Practice questions on Genetic Factors 2
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- 2What does research suggest about aggression?True / false
- 3What techniques have been used to measure aggression?Fill in the list
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